I have Raynaud's, and my blood pressure is usually a little low. I also have Hashimoto's (autoimmune hypothyroidism), so that certainly contributes. I've never heard of a link between Sjogren's and blood pressure, but it's a crazy disease so anything is possible.
Raynaud's is, unfortunately, incredibly common. It likes to piggy-back with other AI diseases; I've never met someone with an autoimmune disease who didn't have Raynaud's, as well.
As far as what you can do, can you tell us what you have done so far?
For the Raynaud's, doctors can't offer us much. Try to stay warm when it's cold and cool when it's hot out. Gloves are important in the winter. I also find carrying a cup of hot herbal tea around in the cooler months helps (and helps w/ my SJS dryness). I don't know of any medical treatments for Raynaud's.
For SJS, most of us are on plaquenil (an anti-malarial) and either evoxac or salagen (meds that encourage salivary flow). Many of us also rely on NSAIDS like ibuprofen to help with aches and pains. We use a lot of eye drops and lotion, stay out of the sun, get lots of rest, eat well, and try to exercise the best we can. Many of us take prednisone when we have flares. Some people benefit from antidepressants. Lots of us have additional AI diseases (I have four) and are on additional treatments for those.
Are you on any medications for SJS yet? If so, what are you taking? Are you seeing a rheumatologist? If so, what has he/she suggested? Which aspects of SJS are you having them most trouble with?